This invention relates to a fire-protection and safety glass panel which serves as a fire-protection panel upon occurrence of fire and as a safety glass panel in an ordinary life.
With recent increase of large-sized architectures such as multistory buildings, department stores, and supermarkets, there is a demand for a fire-protection and safety glass panel having dual functions as a fire protection panel for shutting out flame and smoke upon occurrence of fire to thereby suppress the spread of the fire at a minimum and as a safety glass panel which is neither shattered into pieces and nor forms a through hole if it is broken in an ordinary life.
A conventional fire-protection panel comprises a low-expansion crystallized glass plate, a borosilicate glass plate, or a wire mesh glass plate (a wire glass plate). On the other hand, a conventional safety glass panel comprises a laminated glass plate including a plurality of soda lime glass plates and a transparent polyvinyl butyral film or films (PVB film) joined by thermocompression bonding to provide a structure which comprises a plurality of glass plates with an intermediate resin layer or layers interposed therebetween. Another conventional safety glass panel comprises a soda lime glass plate with an antishattering film applied on a surface thereof. However, a fire-protection and safety glass panel which has both a fire protection function and a safety function has not yet been known.
If the safety glass panel is heated upon occurrence of fire, it is thermally cracked to form a through hole. In particular, when the above-mentioned laminated glass plate is heated, the PVB film is decomposed to produce a combustible gas. The gas is blown to a nonheated side and inflamed to accelerate the spread of the fire. For thermocompression bonding of the transparent film, a large-sized heating furnace is required so that the laminated glass plate is completely received therein. Furthermore, when a plurality of the glass plates have different thermal expansion coefficients and the PVB film is thermocompression bonded to the glass plates to provide an intermediate resin layer therebetween, a warp is caused to occur due to the difference in contraction of the glass plates during cooling.
On the other hand, the low-expansion crystallized glass plate or the borosilicate glass plate used as the fire protection panel is easily broken due to mechanical impact in the ordinary life to be shattered into pieces or dropped off. The wire mesh glass plate has a safety effect to some extent. However, if the glass plate is subjected to a great impact, for example, due to strong collision of a human body, a wire mesh will be cut off to form a through hole. In this event, the human body may be injured.
There are known incombustible transparent films such as a fluoric resin film. However, this film is very expensive and slightly opaque. Accordingly, it is difficult to obtain a laminated glass panel having a high transparency. In addition, this film is poor in evenness. When this film is adhered to the glass plate, air bubbles easily enter into a gap formed therebetween. It is therefore difficult to obtain a transparent appearance.